The present invention relates to an automatic analysis apparatus for performing clinical examinations. More particularly, the invention is concerned with an automatic analysis apparatus which is adapted to perform an analysis for clinical examination by selecting a reaction tube composed of a material to which a reagent does not stick or adhere.
Automatic analysis equipment for clinical examination known heretofore, there may be have included a table for holding samples, a table for holding reagents, a reaction tube into which a sample and a reagent are pipetted, a table for holding a plurality of reaction tubes, a sample pipetting mechanism, a reagent pipetting mechanism, a light intensity measuring instrument for measuring absorbance of a liquid reactant within the reaction tube, a cleaning, mechanism for cleaning the reaction tube, and a computer for controlling operations of the whole system. In operation of the analysis apparatus, a predetermined amount of a sample is pipetted into a reaction tube, followed by pipetting of a predetermined amount of a reagent into the tube, whereupon reaction of the sample with the reagent is conducted. After lapse of a predetermined time, light absorbance of the liquid reactant is measured to analyze concentrations of components of the sample. After completion of the analysis, the used reaction tube is cleaned by the cleaning mechanism for making it reusable in a succeeding analysis. In general, in the automatic analysis apparatus for the clinical examination, the reaction tubes are cleaned after analysis and used repeatedly.
In the automatic analysis apparatus, the reaction tube is often used again for the analysis of an item which differs from that of the preceding analysis or measurement. In that case, when the reagent used for the item subject to the preceding analysis is to be employed in the reaction with a sample concerning the item designated for the succeeding analysis, and when the reagent used in the preceding analysis can not completely be removed from the reaction tube notwithstanding the cleaning performed at the final stage, an error may occur in the data of measurement. Avoidance of such an error relies on the judgement of the clinical examiner. Namely, the phenomenon of adhesion of the reagent to the reaction tube is suppressed to a possible maximum by avoiding the use of the combination of the reagent tube and the sample or reagent which may give rise to the adhesion phenomenon. Further, the analysis for the item which tends to bring about an error or abnormality in the measurement data is usually performed separately after measurements or analyses for all the other items have been completed.
It is also conceivable that some chemical reaction may take place between a reagent and the reaction tube. In that case, the analysis is performed by replacing the concerned reaction tube with a tube made of glass which is intrinsically immune to the chemical reaction. Upon completion of the analysis, the glass tube is cleaned by using a cleaning agent and rinsed with water for reuse in a succeeding analysis.
In the automatic analysis apparatus or equipment, it has been a general practice to use repeatedly a reaction tube made of a plastic material by cleaning it after the analysis for reuse in the succeeding analysis because plastic reaction tubes are expensive. However, when use is limited to plastic reaction tubes, there arises problems that the reagent can not completely be removed solely by the cleaning and that reaction may take place between the plastic tube and the reagent. In case a reagent component adheres fixedly to the reaction tube, the former will partake in the reaction for the succeeding analysis and contribute to color development. Consequently, the reaction rate becomes higher when compared with the case in which the reaction tube as used is utterly free of the sticking reagent, thus incurring erroneous measurement result. Moreover, in the case of a colloidal reaction such as the thymol turbidity test (TTT), for example, the reagent is likely to react with the plastic test tube, causing an error in the resulting data. In this manner, the measurement data made available with the conventional automatic analysis apparatus are susceptible to significant influence of selected combinations of the reaction tube materials and the reagents, incurring errors in the result of the analyses.
In order to avoid the inconveniences mentioned above, it is necessary to replace all of the plastic reaction tubes with tubes made of a material that is insusceptible to reaction with the reagents, as in the case of the thymol turbidity test (TTT). However, such replacement requires additional time, whereby the analysis process is undesirably elongated. Besides, glass tubes are more expensive than plastic tubes, thus involving an increase in the running cost.
Moreover, when the reagent adheres fixedly to the reaction tube, difficulty will be encountered in evading the adverse influence to the succeeding analysis performed by the same tube even when the latter is cleaned sufficiently. Under the circumstances, it will become necessary to limit the items to be analyzed by the apparatus or to select the reagents to be used in dependence on the materials of the reaction tubes.